The present invention relates generally to a support assembly where the individual support members can be slide mounted longitudinally relative to one another, and be releasably held in selected positions. More particularly, the present invention relates to such a support assembly particularly adapted for use in a musical instrument support stand.
There has recently been developed by the assignee of the present patent application a quite convenient musical support stand for trumpets, trombones, or other instruments. Such a support stand comprises a base member in the form of a tripod and a telescoping post extending upwardly from the tripod. A bell shaped support member, adapted to engage the mouth of the instrument to be supported is mounted to the upper telescoping member of the post. The bell shaped member can be moved vertically along the length of the upper telescoping member to the desired height. This support stand can be easily assembled and adjusted to conveniently support the instrument at a desired location along the length of the post.
One of the key considerations in the design of such a support stand is the manner in which the two post members and the bell support can be adjusted relative to one another and then held in place. One solution is to provide the proper degree of frictional engagement between the components that are slide mounted relative to one another so that a person would normally be able to overcome the frictional force to move the components to the desired positions. However, once in the desired positions, there would be sufficient frictional force to cause the components to remain in those positions during normal size. However, this is a less than totally desirable compromise. A more desirable approach would be to provide a positive positioning or locking device or devices so that little force is required to move the components to the desired position, and once in place, the components are held quite reliably and firmly in such position.
There are in the prior art a number of releasable locking or positioning devices which can be used for a variety of applications. A search of the U.S. Patent literature has disclosed a number of such devices and these are given below.
U.S. Pat. No. 185,105, How, illustrates a tool holder where there is a shank of a tool having an end section that is flattened along one side, and a second section adjacent to the end having side recessed portions. The end of this shank member can be inserted into the tool holder and rotated to a location to keep the members joined together. When the flattened end portion of the shank is out of specific alignment with the tool holder, it cannot be withdrawn from the tool holder.
U.S. Pat. No. 808,992, Lawson, discloses an extendable handle where there are two telescoping members. One of the members has a pair of concentric tubular portions defining an annular passageway in which the other telescoping members fit. At one end of one of the members, there is a rotatable cam which moves against mating cam members to move the cam members outwardly into locking relationship to hold the telescoping members in place.
U.S. Pat. No. 2,168,188, Bernhard, shows a collapsable umbrella having a telescoping handle. There are a pair of rotatable discs which can be moved to lock the handle in place.
U.S. Pat. No. 2,397,382, Smith, shows a locking device where two members can be attached end to end. One of the members has a socket which has a somewhat oval cross section. The other member has a mating stud which fits into the socket, with the stud also having an oval configuration. By turning the members relative to one another, the stud comes into wedging engagement with the socket.
U.S. Pat. No. 3,515,418, Nielsen, Jr., discloses a locking mechanism for a telescoping assembly where there is a cam sleeve mounted around a rotatable cam member that is attached to one end of one of the telescoping members. By rotating the member having the cam, the sleeve is pushed outwardly into wedging engagement with outer telescoping member.
U.S. Pat. No. 3,825,359, Fulton, shows a releasable mounting device for cylindrical objects such as electrical circuit elements. There's a base having an internal opening to receive the member. At the end of the base, there is a locking ring with an eccentric annular inner surface. By turning the ring relative to the base, it moves out of alignment with the base and thus presses against the member to lock it in place.
U.S. Pat. No. 3,833,012, McAllister, discloses an adjustable tent pole. There is a pair of axially adjustable telescoping tubes, the smaller of which carries a plug with a freely rotatable eccentrically mounted knurled ring thereon. The ring is eccentrically mounted on an eccentric axis of rotation. To lock the two tubes together, the two tubes are tilted with respect to each other so that the ring is pressed against the outer tube. The two tubes are then rotated so that the ring moves eccentrically to press against the outer tube and thus wedge it in place.
U.S. Pat. No. 3,836,273, Gutman, et. al., discloses a detachable telescopic joint where the outer tubular member has three sections. The middle section is circular, and the two outer sections are oval shaped. With the longer axes of the two oval shaped sections being at right angles to one another.
U.S. Pat. No. 3,942,826, Lester, discloses a lock assembly for connecting two members, such as two tubes. One member has a socket that is stepped, and the other member has a stud with two stepped circular sections to fit into the socket. However, the center axis of the sockets and the stud sections are off-set so that by rotating the two tube members, the two tube members come into locking engagement.
U.S. Pat. No. 4,231,574, Williams, shows an arrangement rather similar to the Lester patent noted above. This permits the two parts of a handle of a cue stick to be connected end to end.
While the above patents do show devices which can be locked one to another by rotating the two components relative to one another, such devices have certain short comings. In some of the devices, the rotation can be in either direction to cause locking engagement. This sometimes leads to confusion as to whether the person is rotating the component so as to bring them more firmly into locking engagement or actually releasing the components. Another difficulty is that with some of the devices which use freely rotating components, engagement of the locking components is not totally reliable.
Accordingly, it is an object of the present invention to provide a releasable locking mechanism of the general type discussed above, which operates reliably and simply. It is a further object to produce such a mechanism which can be conveniently and economically manufactured and assembled.